Close beside the path they were following a bird suddenly chirped from the branch of a tree.

【翻译】靠近他们行走的小路边上，一只鸟突然从树枝上叫了一声。

【分析】Close beside the path （地点状语）they were following（定语从句，修饰path） a bird （主语）suddenly chirped from the branch of a tree（谓语）.

理解该句的关键是：they were following 是the path 的定语从句。follow the path： 沿路而行。